Both following Hegel and opposed to him, Heidegger proposes Descartes as the moment when the “sovereignty of the subject” is established (in philosophy), inaugurating the discourse of modernity. This supposes that man, or rather the ego, is determined and conceived of as subject (subjectum).

Doubtless, from one text to another, and sometimes even within the same “text” (I am primarily referring here to the Nietzsche of 1939–46), Heidegger nuances his formulation. At one moment he positively affirms that in Descartes’s Meditations (which he cites in Latin) the ego as consciousness (which he explicates as cogito me cogitare) is posited, founded as the subjectum (that which in Greek is called the hypokeimenon). This also has the correlative effect of identifying, for all modern philosophy, the hypokeimenon and the foundation of being with the being of the subject of thought, the other of the object. At another moment he is content to point out that this identification is implicit in Descartes, and that we must wait for Leibniz to see it made explicit (“called by its own name”) and reflected as the identity of reality and representation, in its difference with the traditional conception of being.

Is this nuance decisive? It would be difficult to find the slightest reference to the “subject” as subjectum in the Meditations, and that in general the thesis that would posit the ego or the “I think/I am” (or the “I am a thinking thing”) as subject, either in the sense of hypokeimenon or in the sense of the future Subjekt (opposed to Gegenstandlichkeit), does not appear anywhere in Descartes. By evoking an implicit definition, one that awaits its formulation, and thus a teleology of the history of philosophy (a lag of consciousness, or rather of language), Heidegger only makes his position more untenable, if only because Descartes’s position is actually incompatible with this concept. This can easily be verified by examining both Descartes’s use of the noun “subject” and the fundamental reasons why he does not name the thinking substance or “thinking thing” “subject.”

The problem of substance, as is well known, appears fairly late in the course of the Meditations. It is posited neither in the presentation of the cogito, nor when Descartes draws its fundamental epistemological consequence (that the soul knows itself “more evidently, distinctly, and clearly” than it knows the body), but rather in the third meditation, when he attempts to establish and to think the causal link between the “thinking thing” that the soul knows itself to be and God, the idea of whom is found immediately in itself as infinite being. But even here it is not a question of the subject. The term will appear only incidentally, in its scholastic meaning, in the “Responses to Objections,” set in the context of a discussion about the real difference between finite and infinite, as well as between thinking and extended substances; a problem for which the Principles will later furnish a properly formulated definition. Along with these discussions, we must consider that which concerns the union between body and soul, the “third substance” constitutive of individuality, the theory that will be elaborated in the “Sixth Meditation” and further developed in the Treatise on the Passions.